*4.12. Antioxidant Activity of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

The antioxidant activity of CS/PVOH/HNT and CS/PVOH/TO@HNT films were evaluated with the diphenyl-1-picrylhydrazyl (DPPH) method. Briefly, 300 mg of each film was cut into small pieces and placed inside dark glass bottles with 10 mL of an ethanolic solution of diphenyl-1-picrylhydrazyl (DPPH) with 40 ppm concentration. A sample with 10 mL of ethanolic DPPH solution without the addition of any film was used as the blank sample. The absorbance of the DPPH solution at 517 nm at 0 h and after 24 h incubation was measured using a Jasco V-530 UV-vis spectrophotometer. For each film, three to five different samples were made and measured. After 24 h incubation of films, the % antioxidant activity was estimated using the Equation (7) reported in previous reports [27,40,41,49].
